The present invention is concerned with a herbicide and, in particular, with the use of an essence oil as a herbicide, as well as a herbicidal composition and a process for controlling growth of unwanted vegetation or weeds.
Previously, standard chemical treatments including hormonal herbicides such as 2, 4-D, a translocated herbicide, were used in controlling weed species, such as for example, common ragwort (Senecio Jacobaea), which is widespread in pastures and which is toxic to livestock. However, such chemicals can generally take 4 to 6 weeks to work and are dependent upon favourable weather conditions for optimum activity.
The inventors of the present invention have surprisingly found that essential oils may be extremely effective as herbicides. The use of essential oils has never previously been disclosed as having a herbicidal effect. The term xe2x80x9cessential oilsxe2x80x9d used in accordance with the present invention refers to compositions comprising a mixture of terpene hydrocarbons and related alcohols, aldehydes and esters.
Therefore, the present invention provides for the use of an essential oil as a herbicide. Advantageously, essential oils, being relatively non-toxic are highly advantageous in terms of their relative ease of application and toxicity profile to non-target organisms.
The essential oil used in accordance with the invention is citronella oil, which may advantageously be included in a herbicidal composition, in an effective amount together with a carrier, diluent or excipient therefor. The major terpene derivative present in citronella oil or citronellol. Terpene compounds and essential oils are significantly more environmentally friendly than previously used agricultural chemicals which have heretofore served as conventional herbicides.
Preferably, the composition comprises the combination of the following ingredients as an approximate percentage of the total composition, 20-30% citronella oil, 5 to 15% surfactant and between 55 to 75% water.
Even more preferably, the herbicidal composition according to the invention comprises 25% essential oil such as citronella oil or the like, 10% surfactant, 65% water or a deviation of plus or minus approximately 10% of said percentage values. Preferably, a bitter of unpalatable compound may be added to the composition so as to render it unpleasant or unpalatable for animal consumption, such as, for example, Bittrex(trademark), or the like.
Improvement in the intensity and speed of action may, advantageously be obtained by, for example, addition of suitable adjuvants to the composition such as for example wetting agents or oils.
The surfactant used in accordance with the present invention is chosen primarily for its function as an emulsifier. Accordingly, any suitable surfactant may be used although preferably an anionic surfactant may be utilised.
The essential oil may be provided in the form of a powder, dust, granules, a solution, emulsion or suspension, with the addition of a liquid and/or solid carriers and/or diluents or the like. Suitable solid carriers include mineral earths, such as for example, bentonite, silica gel, talc, attapulgite, limestone. Therefore, according to a further aspect of the invention there is provided a herbicidal agent comprising citronella oil, or the like, absorbed, dissolved or emulsified into a solid or liquid carrier. Preferably, when the carrier is a solid it can itself dissolve in a liquid carrier, such as water. Thus advantageously the herbicidal agent may be supplied in a convenient storage form and may subsequently be dissolved in a suitable amount of water for subsequent application, by spraying or the like.
The composition may be applied in a manner known to those in the art, for example, with water as the carrier in spray mixture volumes.
According to a further aspect of the invention there is provided a method for controlling the growth of weeds at a locus which method comprises applying thereto an effective amount of citronella oil and more preferably, applying an effective amount of a herbicidal composition or agent according to the invention.
The citronella oil and also the composition used in accordance with the invention has, advantageously, been found to be particularly effective against broad leaved weed species such as docks, nettles and thistles, although it is particularly effective against common ragwort which is toxic to livestock.